Vehicular turn signal indicator systems using light emitting diodes (LEDs), power consumption of which is lower than that of light bulbs, have become commercially practical. An example of such systems is shown in FIG. 5. The system includes two LED lamps: a left rear LED lamp 800a for a left rear turning signal indicator and a right rear LED lamp 800b for a right rear turning signal indicator. When a hazard warning switches 620a and 620b are turned on, a flashing control circuit 500c performs control for flashing front indicator lamps 810a, 810b and the rear LED lamps 800a, 800b. 
In this system, a current flowing through a current detecting resistor 520 does not significantly vary when an LED is disconnected. Therefore, it is difficult to detect the disconnection of the LED.
To properly detect the disconnection, current correction circuits 710a, 710b are connected. The current correction circuit 710a, 710b supply a pseudo current to the LEDs so that a proper size of current for the disconnection detection flows through the resistor 520. A disconnection detecting circuit is provided for each LED lamp 800a, 800b. The disconnection detecting circuit outputs a signal indicative of the disconnection to a current shutoff circuit 700a, 700b. When the signal is inputted, the shutoff circuit 700a, 700b shuts off the current supply to the current correction circuit 710a, 710b. 
With the above configuration, the disconnection detection is properly performed for the indicator lamps constructed of LEDs. However, the current correction circuits 710a, 710b consume a large amount of power and produce a large amount of heat.